.border-one(@color: rgba(7,17,27,0.1)){   /* 变量以@开始,必须初始化一个值如  @color: red */
  position: relative;
  &:after{
  	display:block;
	position:absolute;
	left:0;
	bottom:0;
	border-top:1px solid @color;
	content: '';
	width:100%;
  }
}
.border-none(){
	&:after{
		display:none;
	}
}
.bg-image(@url: 'brand'){
	background-image: url('@{url}@2x.png');                                      /* mixin中的字符串拼接'@{url}@2x.png' */
	@media (-webkit-min-device-pixel-radio:3),(min-device-pixel-radio:3){
		background-image: url('@{url}@3x.png');
	}
}